1. Field of the Invention
This invention relates to a feed bar driving system in a transfer press machine, and more particularly to improvements in a system for moving feed bars.
2. Description of the Prior Art
Feed bars in a transfer press machine are tridimensionally moved by advance-return motions performed in the order of advance, stop, return and stop, motions of approaching the feed bars to each other to clamp a work or separating the feed bars from each other to unclamp the work and motions of lifting or lowering the feed bars when the work is carried in or out from a molding position. These motions are realized by an advance-return device, a clamp-unclamp device and a lift-lowering device, respectively.
Out of the above mentioned devices, as the advance-return device, a device, wherein a planetary gear mechanism and a crank mechanism are combined to each other, or a cam type device have heretofore been used. However, there have been such disadvantages that the former is complicated in mechanism, and moreover, vibrations due to backlashes of gears tend to be generated, and the latter is troublesome in manufacturing a cam.
The conventional clamp-unclamp device is constituted by a cam mechanism, a plurality of gear mechanisms and the like, and these cam mechanism, the gear mechanisms and the like are adapted to transmit a driving force through contacts between the members.
In consequence, each of the conventional devices is provided with a multiplicity of portions where the members are brought into contact with each other to transmit the driving force, whereby, while the driving force inputted from a cam member connected to a driving shaft of a slide is passed through a driving force transmission route constituted by the cam mechanism, gear mechanism and the like and transmitted to a member for holding the feed bars, a time lag occurs due to backlash between the aforesaid members, thus presenting such a disadvantage that the device as a whole is low in operating efficiency. Because of this, if the vertically moving speed of the slide is increased in order to improve the press operating efficiency, then the approaching-separating operations of the feed bars cannot follow the vertical movement of the slide, thus presenting the disadvantage of that the vertically moving speed of the slide cannot be highly increased.